This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-187018, filed Jun. 30, 1999, the entire contents of which are incorporated herein by reference.
This invention relates to a semiconductor device provided with a capacitor wherein a ferroelectric film is employed as a dielectric film, and to a method for manufacturing such a semiconductor device.
A ferroelectric RAM provided with a capacitor wherein a ferroelectric film is employed as a capacitor dielectric film has been attracting attentions as a high-speed readable and writable RAM.
In a process of forming a capacitor of a ferroelectric RAM, a step of patterning a ferroelectric film constituting a capacitor dielectric film is required. Conventionally, the patterning of a ferroelectric film of such as Pb(Zr, Ti)O3 is usually performed by means of plasma dry etching where Ar and C12 are employed as an etching gas.
However, when the patterning of a ferroelectric film is performed by means of the dry etching of this kind, the ferroelectric film is inevitably exposed to plasma, thereby raising various problems that the ferroelectric film may be damaged or the dielectric property of the ferroelectric film may be deteriorated, thus resulting in a decrease of the number of repetition of writing in the ferroelectric RAM.
Therefore, an object of this invention is to provide a semiconductor device provided with a capacitor wherein a ferroelectric film is employed as a dielectric film, and the ferroelectric film is prevented from being deteriorated.
Another object of this invention is to provide a method of manufacturing a semiconductor device provided with a capacitor with a ferroelectric film being employed as a dielectric film, wherein in the step of working the ferroelectric film, the ferroelectric film is prevented from being damaged and the dielectric property of the ferroelectric film is inhibited from being deteriorated.
According to this invention, there is provided a semiconductor device comprising a semiconductor substrate, and a plurality of capacitors formed on the semiconductor substrate, wherein the plurality of capacitors comprise a plurality of lower electrodes formed on the semiconductor substrate, a ferroelectric film formed continuously covering the plurality of lower electrodes, and an upper electrode formed on the surface of the ferroelectric film, each of the plurality of capacitors being formed for each of the plurality of lower electrodes.
Further, according to this invention, there is also provided a semiconductor device comprising a semiconductor substrate, an insulating film having a hole and formed on the semiconductor substrate, and a capacitor formed on the insulating film, wherein the capacitor comprises a lower electrode formed on a bottom portion of the hole of the insulating film, a ferroelectric film filled in the hole, and an upper electrode formed on the surface of the ferroelectric film.
Further, according to this invention, there is also provided a method of manufacturing a semiconductor device, which comprises the steps of:
forming an interlayer insulating film on a semiconductor substrate;
forming an insulating layer on the interlayer insulating film;
forming a plurality of holes in the insulating film;
filling a lower electrode in each of the holes to form a plurality of lower electrodes;
forming a ferroelectric film on the insulating layer as well as on the plurality of lower electrodes;
forming a conductive layer on the ferroelectric film; and
patterning the conductive layer and the ferroelectric film to form a capacitor dielectric film and an upper electrode covering the plurality of lower electrodes, thereby forming a capacitor for each of the plurality of lower electrodes.
Further, according to this invention, there is also provided a method of manufacturing a semiconductor device, which comprises the steps of:
forming a first insulating film on a semiconductor substrate;
forming a first conductive layer and a dummy film successively on the first insulating film;
forming a dummy film pattern by patterning the dummy film;
forming a lower electrode by etching the first conductive layer with the dummy film pattern being employed as a mask;
forming a second insulating film on the first insulating film as well as on the dummy film;
removing a surface region of the second insulating film to expose a surface of the dummy film pattern;
forming a first hole having a bottom exposing the lower electrode by removing the dummy film pattern;
forming a ferroelectric film filling the first hole; and
forming an upper electrode on the ferroelectric film thereby forming a capacitor.
Furthermore, according to this invention, there is also provided a method of manufacturing a semiconductor device, which comprises the steps of:
forming an insulating film on a semiconductor substrate;
forming a first hole in the insulating film;
forming a conductive layer on the insulating layer as well as on an inner wall of the first hole;
forming a dummy film filling the first hole having the conductive layer deposited on the inner wall;
removing an exposed portion of the conductive layer thereby forming a lower electrode consisting essentially of the portion of the conductive layer that remains on a bottom of the first hole;
removing the dummy film to expose the lower electrode, thereby forming a second hole having a sidewall exposing the insulating film and a bottom exposing the lower electrode;
forming a ferroelectric film filling the second hole; and
forming an upper electrode on the ferroelectric film thereby forming a capacitor.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.